Abstract
Using near-infrared speckle interferometry we have obtained
resolved JHK-photometry for the components of 58 young binary systems.
From these measurements, combined with other data taken from literature,
we derive masses and particularly mass ratios of the components.
We use the J-magnitude as an indicator for the stellar luminosity and assign
the optical spectral type of the system to the primary.
On the assumption that the components within a binary are coeval we can then
also place the secondaries into the HRD and derive masses and mass ratios
for both components by comparison with different sets of current theoretical
pre-main sequence evolutionary tracks. The resulting distribution of mass
ratios is comparatively flat for
, but depends on assumed
evolutionary tracks. The mass ratio is neither correlated with the primary's
mass or the components' separation. These findings are in line with the
assumption that for most multiple systems in T associations the components'
masses are principally determined by fragmentation during formation and
not by the following accretion processes.
Only very few unusually red objects were newly found among the detected
companions.This finding shows that the observed overabundance of binaries
in the Taurus-Auriga association compared to nearby main sequence stars
should be real and not the outcome of observational biases related to
infrared observing.